1. Field of the Invention
This invention relates to automatic fuel ignition systems, and more particularly, to an automatic fuel ignition system employing electronic leak detection for a valve.
2. Description of the Prior Art
Automatic fuel ignition systems include a control circuit which provides sequential operation of valves of the system. For example, in pilot ignition systems, the control circuit responds to a request signal, typically the application of power to the control circuit in response to operation of a thermostatically-controlled switch, to effect the operation of a pilot valve to supply fuel to a pilot outlet. The control circuit also enables an ignition circuit to generate ignition sparks for igniting the fuel to establish a pilot flame. When a pilot flame is established, the control circuit operates a main valve which supplies fuel to a main burner for ignition by the pilot flame.
In such systems the presence or absence of a flame at the pilot outlet is generally used to effect the sequencing operations provided by the control circuit and to enable various checks to assure fail-safe operation of the system to prevent inadvertant operation of the pilot and main valves. Thus, a leak condition for the pilot valve, for example, could interrupt the normal sequencing operations of the system which permit fail-safe operation of the system. Moreover, for a leak condition for the pilot valve, fuel will be continously supplied to the pilot outlet, wasting fuel and producing a potentially hazardous condition.
In the U.S. Pat. No. 3,840,322 of Philip J. Cade, there is disclosed electrical control circuitry for use in an automatic fuel ignition system and which is operable to effect lock out of the system whenever a pilot flame is provided at a burner prior to the operation of a fuel valve of the system, indicative of a leak condition for the pilot valve. However, the system does not provide for a restart of the ignition interval upon detection of such condition. Thus, in the event of a line voltage interruption of a very short duration, wherein the pilot flame may not be extinguished before power is restored to the system, the system may be locked out. Accordingly, for such condition, manual reset of the system would be required before the system can be reactivated, even though the pilot valve may be functioning properly.
Thus, it would be desirable to have an automatic fuel ignition system which automatically distinguishes between a leak condition for the pilot valve and a line voltage interruption which permits the pilot flame to remain established upon momentary deactivation of the system, and which permits recycling of the system following a fast line interruption, but effects the shut down of the system for a leak condition for the valve.